Analysis And Recovery Of Indium In Waste Liquid Crystal Display

Rare metal Indium, which was mostly used in the production of ITO(Indium Tin Oxide) conductive glass, is in large dosage but with less reserves. As the main part of Liquid Crystal Display(LCD) screen, ITO conductive glass has been widely used with the rapid development of electronic industry. The rejection of electronic products caused a large amount of waste electronic products including waste LCDs. There’s contains very few Indium contained in one piece of Waste LCD, but the great number of rejecting and manufacturing makes it giant. All these become an important Indium secondary resource. Recover Indium from waste LCDs have both environmental and resource benefits. At present, there is few comprehensive utilization of Indium in waste LCDs, and no report on mature or large-scale technology.This research focused on the recover and reuse of Indium contained in wasted LCDs, the conditions of analyzing, leaching and recovering Indium from waste LCDs were respectively discussed in this paper:(1) A method of Indium analyzing in waste LCDs was established by improving Chinese National Standard, and a new pre-treatment method was studied. The recovery of standard addition was 95.02%-105.50% with precision of 6.51% RSD(n=10). The linear range was at 0~2.5μg/ml.(2) The influence of different facts were investigated by single factor and orthogonal tests and the optimum process of leaching conditions were determined: no-smashed, HNO3(8mol/L), liquid-solid ratio(4:5). Leaching samples in at room temperature for 48 h with H2O2(20% of the mass of samples) or at 100℃ for 3h, the leaching rate can be reached to 75.62% and 68.42% respectively.(3)The influence of different conditions of extracting-re-extracting were investigated. The proper extracting-re-extracting process was set up. When the volume ratio of P204 to kerosine was 5:5, the p H was 2, the O/W was 1:3 and the time of concussion was 4min, the extracting rate of Indium and Tin can be reached to 97.03% and 76.81% respectively. After that, when the concentration of HCl was 4mol/L, the water/organic ratio was 1:4, the re-extract time was 2min and re-extract series was 2, the re-extracting rate of Indium and Tin can be reached to 97.58% and 21.48% respectively.This research was baesd on the actual situation of Chinese electric wastes industry. The process has the characteristics of short process, low energy consumption, low reagent consumption, economic practical and environment friendly. The recover rate of Indium can be reached above 70% and it has a certain prospect of industrialization.